Exam 22: Magnetic Forces and Magnetic Fields

A long solenoid (diameter = 5.0 cm)is wound with 960 turns per meter of thin wire through which a current of 300 mA is maintained.A wire carrying 12 A is inserted along the axis of the solenoid.What is the magnitude of the magnetic field at a point 2.0 cm from the axis?

Three coplanar parallel straight wires carry equal currents I to the right as shown below.The current in the upper two wires is directed to the right,but the current in the bottom wire is directed to the left.Each pair of wires is a distance a apart.The direction of the magnetic force on the middle wire

When a ferromagnetic material that has been magnetized is brought to a temperature greater than the Curie temperature,what happens to its residual magnetism.

What is the magnetic force on a 2.0-m length of (straight)wire carrying a current of 30 A in a region where a uniform magnetic field has a magnitude of 55 mT and is directed at an angle of 20 $\degree$ away from the wire?

A straight wire is bent into the shape shown.Determine the net magnetic force on the wire.

What current must be maintained in a square loop (50 cm on a side)to create a torque of 1.0 N . m about an axis through its center and parallel to one of its sides when a magnetic field of magnitude 70 mT is directed at 40 $\degree$ to the plane of the loop?

What value of B should be used in a velocity selector to separate out 2.0-keV protons if E is fixed at 80 kV/m?

Two long parallel wires are separated by 2.0 cm.The current in one of the wires is three times the other current.If the magnitude of the force on a 2.0-m length of one of the wires is equal to 60 $\mu$ N,what is the greater of the two currents?

A long wire is known to have a radius greater than 4.0 mm and to carry a current uniformly distributed over its cross section.If the magnitude of the magnetic field is 0.285 mT at a point 4.0 mm from the axis of the wire and 0.200 mT at a point 10 mm from the axis,what is the radius of the wire?

A segment of wire carries a current of 25 A along the x axis from x = -2.0 m to x = 0 and then along the z axis from z = 0 to z = 3.0m.In this region of space,the magnetic field is equal to 40 mT in the positive z direction.What is the magnitude of the force on this segment of wire?

A proton with a kinetic energy of 0.20 keV follows a circular path in a region where the magnetic field is uniform and has a magnitude of 60 mT.What is the radius of this path?

The figure shows the orientation of a flat circular loop consisting of 50 closely wrapped turns each carrying a current I.The magnetic field in the region is directed in the positive z direction and has a magnitude of 50 mT.The loop can turn about the y axis.If $\theta$ = 20 $\degree$ ,R = 0.50 m,and I = 12A,what is the magnitude of the torque exerted on the loop?

The figure shows a cross section of three parallel wires each carrying a current of 20 A.The currents in wires A and B are out of the paper,while that in wire C is into the paper.If the distance R = 5.0 mm,what is the magnitude of the force on a 2.0-m length of wire A?

A circular loop (radius = 0.50 m)carries a current of 3.0 A and has unit normal vector of ( $2 \tilde { \mathbf { i } } - \tilde { \mathbf { j } } + 2 \tilde { \mathbf { k } }$ )/3.What is the x component of the torque on this loop when it is placed in a uniform magnetic field of ( $2 \tilde { \mathbf { i } } - 6 \tilde { \mathbf { j } }$ )T?

A velocity selector uses a fixed electric field of magnitude E and the magnetic field is varied to select particles of various energies.If a magnetic field of magnitude B is used to select a particle of a certain energy and mass,what magnitude of magnetic field is needed to select a particle of equal mass but twice the energy?

A straight wire carries a current of 40 A in a uniform magnetic field (magnitude = 80 mT).If the force per unit length on this wire is 2.0 N/m,determine the angle between the wire and the magnetic field.

A superconducting wire carries a current of 1.0 * 10⁴ A.Find the magnetic field at a distance of 1.0 m from the wire.

A deuteron is accelerated from rest through a 10-kV potential difference and then moves perpendicularly to a uniform magnetic field with B = 1.6 T.What is the radius of the resulting circular path? (deuteron: m = 3.3 * 10 ^{- 27} kg,q = 1.6 *10 ^{- 19} C)

An electron has a velocity of 6.0 *10⁶ m/s in the positive x direction at a point where the magnetic field has the components B_x = 3.0 T,B_y = 1.5 T,and B_z = 2.0 T.What is the magnitude of the acceleration of the electron at this point?

In the figure,if a = 2.0 cm,b = 4.0 cm,and I = 2.0 A,what is the magnitude of the magnetic field at point P?